1. Field of the Invention
The present invention relates to a high frequency amplifier circuit. More particularly, it relates to a high frequency amplifier circuit and a microwave integrated circuit used in microwave, sub-millimeter wave and millimeter wave bands.
2. Description of the Related Art
With the development of radio communications technologies, higher radio frequencies have come to be used and recently millimeter waves and sub-millimeter waves having frequencies beyond 20 GHz have been in use.
In amplifiers and MMIC (monolithic microwave integrated circuit) used at extremely high frequencies beyond 20 GHz, dispersion in the characteristics of active devices and dispersion in passive circuits greatly affect the circuit performance, thus making it difficult to achieve a high yield of production and presenting a hurdle against the effort of cost reduction. Also, in the stage of design or development, it is difficult to exactly determine the characteristics of active devices (equivalent circuit parameters) and the model parameters of passive circuits, and therefore target specifications can hardly be satisfied in a single trial fabrication. This situation has also resulted in a significant increase in the development cost. Also, because it takes a long period of time to develop one type of product, it has been difficult to allow small-lot production of various products having different characteristics such as frequency, gain and output power.